减压阀是利用膜片、弹簧、活塞等敏感元件改变阀瓣与阀座之间的间隙，当介质通过时产生节流，()而使其减压的阀门。

A．温度降低

B．压力升高

C．压力下降

D．温度升高

Border Gateway Protocol(BGP) is inter-autonomous system (96) protocol. BGP is based on a routing method called path vector routing. Distance vector routing is not a good candidate for inter-autonomous system routing because there are occasions on which the route with the smallest (97) count is not the preferred route. For example, we may not want a packet through an not secure even though it is the shortest route. Also, distance vector routing is unstable due to the fact that the routers announce only the number of hop counts to the destination without actually defining the path that leads to that (98) . A router that receives a distance vector advertisement packet may be fooled if the shortest path is actually calculated through the receiving router itself. Link (99) routing is also not a good candidate for inter-autonomous system routing because an Internet is usually too big for this routing method. To use link state routing for the whole internet would require each router to have a huge link state database. It would also take a long time for each router to calculate its rousting (100) using the Dijkstra algorism.

（99）是（）

A.status

B.search

C.state

D.research